How do we know John the Baptist is the Elijah that was to come?

In Matthew 11:11-14, Jesus directly states that John the Baptist is the fulfillment of the prophecy regarding Elijah's return. This declaration showcases the continuity between the Old and New Testaments, where John fulfills the role of the messenger who prepares the way for the Lord. The disciples' confusion about Elijah in Matthew 17:10-12 is clarified by Jesus, who confirms that John was indeed the anticipated figure. This rich intertwining of prophecy and fulfillment demonstrates God's sovereign plan through history, culminating in Christ.